linux-kernel - Re: [PATCH] mm/page_isolation: don't putback unisolated page

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Message-ID: <febcceaa-7d94-c3a3-c683-7a8694981b47@nvidia.com>
Date:   Wed, 8 Sep 2021 15:42:27 -0700
From:   John Hubbard <jhubbard@...dia.com>
To:     David Hildenbrand <david@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org
Cc:     iamjoonsoo.kim@....com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/page_isolation: don't putback unisolated page

On 9/7/21 2:56 AM, David Hildenbrand wrote:
...
>> If this can be handled gracefully, then I'd rather go with VM_WARN_ON.
>> Maybe even WARN_ON_ONCE?
>>
> 
> I think either VM_BUG_ON() or VM_WARN_ON() -- compiling the runtime checks out -- should be good 
> enough.
> 
> I'd just go with VM_BUG_ON(), because anybody messing with __isolate_free_page() should clearly spot 
> that we expect the current handling. But no strong opinion.
> 

If in doubt, WARN*() should be preferred over BUG*(). There's a pretty long
history of "don't kill the machine unless you have to" emails about this, let
me dig up one...OK, maybe not the best example, but the tip of the iceberg:

http://lkml.iu.edu/hypermail/linux/kernel/1610.0/00878.html

thanks,
-- 
John Hubbard
NVIDIA